Apparatus and method for single substrate processing using megasonic-assisted drying

ABSTRACT

In a method for treating a semiconductor substrate, a single substrate is positioned in a single-substrate process chamber and subjected to wet etching, cleaning and/or drying steps. The single substrate may be exposed to etch or clean chemistry in the single-substrate processing chamber as turbulence is induced in the etch or clean chemistry to thin the boundary layer of fluid attached to the substrate. Megasonic energy and/or disturbances in the chamber surfaces may provide the turbulence for boundary layer thinning. According to another aspect of a method according to the present invention, megasonic energy may be directed into a region within the single-substrate process chamber to create a zone of boundary layer thinning across the substrate surface, and a single substrate may be translated through the zone during a rinsing or cleaning process within the chamber to optimize cleaning/rinsing performance within the zone.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 10/826,458 (APPM/010533.C1), filed Apr. 16, 2004, which is acontinuation of co-pending U.S. patent application Ser. No. 10/010,240(APPM/010533), filed Dec. 7, 2001, issued U.S. Pat. No. 6,726,848. Eachof the aforementioned related patent applications is herein incorporatedby reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the field of surface preparationsystems and methods for semiconductor substrates and the like.

2. Description of the Related Art

In certain industries there are processes that must be used to bringobjects to an extraordinarily high level of cleanliness. For example, inthe fabrication of semiconductor substrates, multiple cleaning steps aretypically required to remove impurities from the surfaces of thesubstrates before subsequent processing. The cleaning of a substrate,known as surface preparation, has for years been performed by collectingmultiple substrates into a batch and subjecting the batch to a sequenceof chemical and rinse steps and eventually to a final drying step. Atypical surface preparation procedure may include etch, clean, rinse anddry steps. An etch step may involve immersing the substrates in an etchsolution of HF to remove surface oxidation and metallic impurities andthen thoroughly rinsing the substrates in high purity deionized water(DI) to remove etch chemicals from the substrates. During a typicalcleaning step, the substrates are exposed to a cleaning solution thatmay include water, ammonia or hydrochloric acid, and hydrogen peroxide.After cleaning, the substrates are rinsed using ultra-pure water andthen dried using one of several known drying processes.

Currently, there are several types of tools and methods used in industryto carry out the surface preparation process. The tool most prevalent inconventional cleaning applications is the immersion wet cleaningplatform, or “wet bench.” In wet bench processing, a batch of substratesis typically arranged on a substrate-carrying cassette. The cassette isdipped into a series of process vessels, where certain vessels containchemicals needed for clean or etch functions, while others containdeionized water (“DI”) for the rinsing of these chemicals from thesubstrate surfaces. The cleaning vessels may be provided withpiezoelectric transducers that propagate megasonic energy into thecleaning solution. The megasonic energy enhances cleaning by inducingmicrocavitation in the cleaning solution, which helps to dislodgeparticles off of the substrate surfaces. After the substrates are etchedand/or cleaned and then rinsed, they are dried. Often drying isfacilitated using a solvent such as isopropyl alcohol (IPA), whichreduces the surface tension of water attached to the substrate surface.

Another type of surface preparation tool and method utilized in thesemiconductor industry is one in which a number of surface preparationsteps (e.g. clean, etch, rinse and/or dry) may be performed on a batchof substrates within a single vessel. Tools of this type can eliminatesubstrate-transfer steps previously required by wet bench technology,and have thus gained acceptance in the industry due to their reducedrisk of breakage, particle contamination and their reduction infootprint size.

Further desirable, however, is a chamber and method in which multiplesurface preparation steps can be performed on a single substrate (e.g. a200 mm, 300 mm or 450 mm diameter substrate), as opposed to a batch ofsubstrates. It is thus an object of the present invention to provide achamber and method for performing one or more surface preparation stepson a single substrate.

SUMMARY OF THE INVENTION

In one aspect of the present invention, a single substrate is positionedin a single-substrate process chamber and subjected to wet etching,cleaning and/or drying steps. According to another aspect of the presentinvention, a single substrate is exposed to etch or clean chemistry inthe single-substrate processing chamber as boundary layer thinning isinduced in the region of the substrate. According to yet another aspectof a method according to the present invention, boundary layer thinningis induced in a zone within the single-substrate process chamber, and asingle substrate is translated through the zone during a process withinthe chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic illustration of a single substrate processingchamber, showing the substrate positioned in the lower interior regionof the chamber.

FIG. 1B is a schematic illustration of a single substrate processingchamber, showing the substrate positioned in the upper interior regionof the chamber.

FIG. 1C is a block diagram illustrating one example of a fluid handlingsystem useable with the chamber of FIG. 1A.

FIG. 1D is a block diagram illustrating a second example of a fluidhandling system useable with the chamber of FIG. 1A.

FIGS. 2A-2C are a sequence of cross-section views of the chamberinterior, illustrating movement of the substrate between the upperinterior region and the lower interior region.

FIG. 3A is a cross-sectional perspective view of a second embodiment ofa single substrate processing chamber showing the fluid manifold in theclosed position. The figure also shows automation provided fortransporting a substrate into, out of, and within the chamber.

FIG. 3B is a cross-sectional perspective view of the single substrateprocessing chamber of FIG. 3A showing the fluid manifold in the openedposition. The transport automation shown in FIG. 3A is not shown in FIG.3B.

FIG. 4 is a cross-sectional perspective view of the upper manifold and aportion of the tank of the second embodiment of FIG. 3A.

FIG. 5 is a cross-sectional side view of the second embodiment of FIG.3A.

FIG. 6 is a perspective view of an end effector of the second embodimentof FIG. 3A. The end effector is shown carrying a substrate.

FIG. 7A is a perspective view of one prong of a second embodiment of anend effector during transport of a substrate.

FIG. 7B is a perspective view showing the end effector of FIG. 7A duringtransport of a substrate into or out of the chamber.

FIG. 7C is a perspective view showing the end effector, substrate andchamber during transport of the substrate into or out of the chamber,with the substrate beginning to make contact with the bottom notch ofthe chamber.

FIG. 7D is a perspective view showing the end effector, substrate andchamber during processing of the substrate within the chamber.

FIG. 7E is a perspective view similar to the view of FIG. 7A showing oneprong of the end effector during processing of the substrate within thechamber.

FIG. 8 is a cross-section view of a chamber according to a thirdembodiment.

DETAILED DESCRIPTION

Three embodiments of single substrate chambers and associated processesare described herein. Each of the described chambers/methods performswet processing steps such as (but not limited to) etching, cleaning,rinsing and/or drying on a single substrate (such as, for example asemi-conductor wafer substrate) using a single chamber. As will beappreciated from the description that follows, such chambers and methodsare beneficial in that each substrate treated using the chamber/methodis exposed to the same process conditions to which the other substratesundergoing the same process are exposed. This yields higher precisionprocessing than seen in a batch system, in which a substrate positionedin one part of a substrate batch may be exposed to slightly differentprocess conditions (such as fluid flow conditions, chemicalconcentrations, temperatures, etc.) than a substrate positioned in adifferent part of the batch. For example, a substrate at the end of alongitudinal array of substrates may see different conditions than asubstrate at the center of the same array. Such variations in conditionscan yield batches lacking in uniformity between substrates.

Single substrate chambers/methods such as those described herein arefurther beneficial in that each substrate is exposed to process fluidsfor a shorter amount of time than is required in batch processing.Moreover, for applications where only a few substrates need processing(e.g. in a prototype engineering context), the individuals requiring theprocessed substrates need only wait a few minutes to receive the treatedsubstrates, rather than waiting a full hour or more for the substratesto be processed in a batch-type chamber. Moreover, the chambers/methodsdescribed herein can be practiced using the same or smaller volumes ofprocess fluids (on a substrate-per-substrate basis) than would be usedin corresponding batch processes.

First Embodiment—Structure

Features of a first embodiment of a single substrate processing chamberare schematically shown in FIGS. 1A-1D. Referring to FIG. 1A, a firstembodiment 2 of a single substrate processing chamber includes a chamber10 having sidewalls 11 defining a lower interior region 12 aproportioned to receive a substrate S for processing, an upper interiorregion 12 b, and an opening 14 in the upper interior region 12 a.

The first embodiment includes a substrate transport device 28. Transportdevice includes an end effector 30 configured to engage a substrate S,and is driven by conventional automation (not shown) to move thesubstrate S through opening 14 into and out of the chamber 10 in anedgewise direction. Transport device 28 is further configured to causeend effector 30 to move the substrate between the lower interior region12 a and the upper interior region 12 b, as described below inconnection with operation of the device.

Transport device 28 may also carry a lid 29 that closes against opening14 when the end effector 30 is lowered. The lid 29 may remain in place,even as the end effector moves the substrate between regions 12 a, 12 bduring processing, and be later withdrawn so that the end effector 30can remove substrate S from the chamber.

The upper end of the lower interior region 12 a may be narrowed toinclude a throat section to increase the velocity of fluid flowingthrough the throat section from the lower section of the chamber. Thebottom of the chamber 10 may be flat or contoured to conform to theshape of the lower edge of the substrate.

Fluid Handling System

The first embodiment 2 is preferably provided with a fluid handlingsystem 26 configured to carry various process fluids (e.g. etch fluids,cleaning fluids, rinse water, etc.) into the lower interior region 12 bof chamber 10.

There are various ways in which the fluid handling system 26 can beconfigured. For example, as shown in FIGS. 1A and 1B. a window 16 may beformed in the lower interior region 12 b and one or more manifolds maybe moveable into place at the window 16 to direct process fluids intothe chamber 10. The manifolds and the window 16 are preferably sealedwithin the fluid handling system 26, a sealed housing that exhaustsfumes, gases, etc. that may be released from the manifolds so as toprevent their escape into the surrounding environment.

A fluid manifold 18 is position able to direct process fluids (e.g.chemistries for etching, and DI water for rinsing) into the lowerinterior 12 a of chamber 10 via window 16. Fluid manifold 18 includes atleast one, but preferably multiple, openings 20 through which fluid isdirected into the chamber 10. The fluid manifold 18 is moveable betweena closed position (FIG. 1A) in which the manifold is oriented to directfluids into the window 16 via openings 20,and an open position (FIG. 1B)in which the openings 20 are positioned away from the window 16. Thefluid manifold 18 may be moveable between the closed and open positionsusing standard automation. Fluid manifold 18 may optionally include amegasonic transducer (not shown) having one or more transducers fordirecting megasonic energy into fluids in the chamber as will bedescribed in greater detail below. For simplicity, the term “megasonictransducer” will be used herein to encompass transducer assembliescomprised of a single transducer or an array of multiple transducers.

A second fluid manifold, which will be referred to as the megasonicsmanifold 22, is provided and includes one or more inlets 24. Like thefluid manifold 18, the megasonics manifold 22 is moveable between aclosed position (FIG. 1B) in which the inlets 24 are oriented to directfluid (e.g. cleaning solutions and DI water for rinsing) from themegasonics manifold 22 through window 16, and an opened position (FIG.1A) in which the inlets 24 are spaced from the window 16, permitting themanifold 18 to be brought into its closed position. The megasonicsmanifold 22 may be moveable between the closed and open positions.

The megasonics manifold 22 includes a megasonic transducer, which mayinclude a single transducer or an array of multiple transducers,oriented to direct megasonic energy into the chamber interior via thewindow. When the megasonic transducer(s) direct megasonic energy intofluid in the chamber, they induce acoustic streaming within thefluid—i.e. streams of microbubbles that aid in removal of contaminantsfrom the substrate and that keep particles in motion within the processfluid so as to avoid their reattachment to the substrate.

Referring to the block diagram of FIG. 1C, the fluid handling system 26may include a system of valves and conduits for directing fluids intothe manifolds 18, 22. A DI water source and a source of etch fluid arefluidly coupled to manifold 18, and valves 19 a, 19 b govern flow ofthese fluids into the manifold 18. It should be appreciated that whilethe etch plumbing is shown configured for injection into a DI waterstream, etch fluid may alternatively be independently directed into themanifold 18. Similarly, valves 23 a, 23 b and associated conduits couplesources of DI water and cleaning fluid to megasonics manifold 22.

The configuration of the fluid handling system shown in FIG. 1C providestwo means for evacuation of fluid from the chamber 10. First, dedicatedsealed containers 31 a, 31 b are provided for rapidly withdrawing fluidsfrom the chamber. Preferably, each sealed container is dedicated to aparticular type of process fluid, e.g. an etch fluid or a cleaningfluid, so as to prevent cross-contamination of process fluids.

Each container 31 a, 31 b is coupled to the chamber 10 by valves 27 a,27 b and associated drain plumbing 29 a, 29 b. Alternatively, the valvesand drain plumbing may couple the sealed containers 31 a, 31 b to themanifolds 18, 22. The sealed containers 31 a, 31 b are maintained atnegative pressure and the valves 27 a, 27 b are kept closed except whenthey are opened for evacuation of the chamber. At the end of the etchprocess, the valve 27 a may be opened, causing rapid removal of the etchfluid into the negative pressure container 31 a for subsequent re-use.This rapid removal of the fluid helps to shear etch solution from thesubstrate surface. It also optimizes uniformity across the substratesurface by creating a sharp transition between exposure of the substrateto the etch solution and separation of the substrate from the bulk etchsolution—thus minimizing surface variations between the top portion ofthe substrate and the lower portion of the substrate. This transitionmay be sharpened further, and the shearing of the etch solution from thesubstrate may be enhanced, by using the end effector to pull thesubstrate into the upper interior region 12 b during the rapid fluidremoval.

The second evacuation means provided in the embodiment of FIG. 1Cutilizes the megasonics manifolds 18, 22, which are moved to the openedposition to dump fluid from the chamber into a drain (not shown).

As another example of a fluid distribution system, a fluid manifold 23as shown in the block diagram of FIG. 1D may be provided with multiplededicated valves 33 a, 33 b, and 33 c feeding process fluids into themanifold 23. In such a configuration, one valve may feed etch solutioninto the manifold, whereas another may feed cleaning solution andanother may feed rinse water. This type of dedicated configuration isdesirable in that it minimizes the number of common plumbing components(i.e. those that are exposed to multiple process chemicals) and thusminimizes the amount of rinsing required for the plumbing betweenprocess steps.

In this example, manifold 23 may include a megasonic transducer, or amegasonic transducer may be positioned in a lower region of the chamber10. The manifold 23 may be fixed or moveable to an opened position for arapid evacuation of the chamber 10. Sealed negative pressure containers31 a, 31 b may also provide an additional means of evacuation asdescribed with respect to the FIG. 1C embodiment. The sealed containers31 a, 31 b may be coupled to the manifold itself, or to the chamber 10as shown in FIG. 1D.

Upper Megasonics

Referring again to FIGS. 1A and 1B, an overflow weir 34 is formed alongthe chamber periphery at the top of the lower interior region 12 a.Process fluid flowing into the chamber from manifolds 18, 22 cascadesinto the weir 34 and into overflow plumbing 35 for recirculation ordisposal. A pair of megasonic transducers 32 a, 32 b, each of which mayinclude a single transducer or an array of multiple transducers, arepositioned at an elevation below that of the weir 34, and are orientedto direct megasonic energy into an upper portion of lower interiorregion 12 a of the chamber 10. Transducer 32 a directs megasonic energytowards the front surface of a substrate, while transducer 32 b directsmegasonic energy towards the rear surface of the substrate.

The transducers are preferably positioned such that the energy beaminteracts with the substrate surface at or just below the gas/liquidinterface, e.g. at a level within the top 0-20% of the liquid in thelower interior 12 a. The transducers may be configured to directmegasonic energy in a direction normal to the substrate surface or at anangle from normal. Preferably, energy is directed at an angle ofapproximately 0-30 degrees from normal, and most preferablyapproximately 5-30 degrees from normal. Directing the megasonic energyfrom transducers 32 a,b at an angle from normal to the substrate surfacecan have several advantages. For example, directing the energy towardsthe substrate at an angle minimizes interference between the emittedenergy and return waves of energy reflected off the substrate surface,thus allowing power transfer to the solution to be maximized. It alsoallows greater control over the power delivered to the solution. It hasbeen found that when the transducers are parallel to the substratesurface, the power delivered to the solution is highly sensitive tovariations in the distance between the substrate surface and thetransducer. Angling the transducers reduces this sensitivity and thusallows the power level to be tuned more accurately. The angledtransducers are further beneficial in that their energy tends to breakup the meniscus of fluid extending between the substrate and the bulkfluid (particularly when the substrate is drawn upwardly through theband of energy emitted by the transducers)—thus preventing particlemovement towards the substrate surface.

Additionally, directing megasonic energy at an angle to the substratesurface creates a velocity vector towards overflow weir 34, which helpsto move particles away from the substrate and into the weir. Forsubstrates having fine features, however, the angle at which the energypropagates towards the substrate front surface must be selected so as tominimize the chance that side forces imparted by the megasonic energywill damage fine structures.

It may be desirable to provide the transducers 32 a, 32 b to beindependently adjustable in terms of angle relative to normal and/orpower. For example, if angled megasonic energy is directed by transducer32 a towards the substrate front surface, it may be desirable to havethe energy from transducer 32 b propagate towards the back surface at adirection normal to the substrate surface. Doing so can prevent breakageof features on the front surface by countering the forces impartedagainst the front surface by the angled energy. Moreover, while arelatively lower power or no power may be desirable against thesubstrate front surface so as to avoid damage to fine features, a higherpower may be transmitted against the back surface (at an angle or in adirection normal to the substrate). The higher power can resonatethrough the substrate and enhance microcavitation in the trenches on thesubstrate front—thereby helping to flush impurities from the trenchcavities.

Additionally, providing the transducers 32 a, 32 b to have an adjustableangle permits the angle to be changed depending on the nature of thesubstrate (e.g. fine features) and also depending on the process stepbeing carried out. For example, it may be desirable to have one or bothof the transducers 32 a, 32 b propagate energy at an angle to thesubstrate during the cleaning step, and then normal to the substratesurface during the drying step (see below). In some instances it mayalso be desirable to have a single transducer, or more than twotransducers, rather than the pair of transducers 32 a, 32 b.

Vapor inlet ports 36, fluid applicators 37, and gas manifold 38 extendinto upper interior region 12 b of the chamber 10. Each is fluidlycoupled to a system of conduits that deliver the appropriate vapors andgases to the ports as needed during processing. The fluid applicators 37are preferably configured to inject a stream or streams of process fluidinto the upper interior region 12 b. It is preferable that the stream(s)of injected fluid collectively extend for a width at least as wide asthe diameter of the substrate, such that fluid may be uniformly appliedat high velocity across the width of the substrate as the substrate ismoved past the stream(s). To this end, the fluid applicators maycomprise a pair of narrow elongate slots in the wall of the upper region12 b of the chamber. It is also preferable that the fluid applicators 37are spaced from the substrate by a very close distance.

First Embodiment—Operation

The system 2 may be used for various processes, including thoserequiring one or more of the steps of wet etching, cleaning, rinsing anddrying. Its use will be described in the context of an etch, clean anddrying process, in which rinses are performed following etching andcleaning. Performance of this combination of steps is efficient in thatit allows multiple steps to be performed in a single chamber, and itminimizes post-treatment particle reattachment since substrates leavethe chamber dry. Moreover, performance of the multiple steps in a singlechamber minimizes buildup of particles and residue in the processchamber, since each time a substrate goes through the sequence ofprocesses, the chamber itself is cleaned and dried. Naturally, variousother combinations of these or other process steps may be performedwithout departing from the scope of the present invention.

Etching

If processing is to begin with an etch procedure, operation of the firstembodiment begins with fluid manifold 18 in the closed position as shownin FIG. 1A. The lower portion 12 a of the chamber 10 is filled withprocess fluids necessary for the etching procedure (for example,hydrofluoric acid (HF), ammonium fluoride and HF, or buffered oxide).These fluids may be injected into a DI water stream entering fluidmanifold 18 (using, for example, the fluid handling configuration shownin FIG. 1C), causing them to flow into the chamber 10 with the DI water.Alternatively, the etch solution may flow directly into manifold 18 andinto chamber, or, if the fluid handling configuration of FIG. 1D isused, the solution may enter manifold 23 and chamber 10 via dedicatedvalve 33 b. In either case, the solution cascading over weir 34 may berecirculated back into the chamber 10 throughout the etch process, suchas by collecting it into a (preferably) temperature-controlled vesseland circulating it back to manifold 18 for re-introduction into thechamber 10. Alternatively, the etch process may be a “one-pass” processin which the overflowing etch solution is directed to a drain fordisposal. As a third alternative, the flow of etch solution may beterminated once the lower portion 12 a of the chamber has been filled.

Substrate S is engaged by end effector 30 and moved into the etchsolution by the substrate transport device 28. Substrate S is positionedin the lower portion 12 a of the chamber, i.e. at an elevation belowthat of the weir 34, so that the substrate is fully immersed in the etchsolution.

In wet processing, a relatively stagnant fluid layer known as a“boundary layer” is typically present at the substrate surface. A thickboundary layer can inhibit the ability of an etch or cleaning solutionto reach and react with the substances that are to be removed from thesubstrate surface. It is thus desirable to minimize the thickness of theboundary layer of fluid attached to the substrate surface so that theetch chemicals can more effectively contact the substrate surface.Boundary layer thinning may be accomplished by inducing turbulence inthe etch fluid using disturbances formed into the sidewalls of thechamber. For example, a random or patterned topography may be machinedinto the side walls so that fluid flowing through the chamber 10 fromthe manifold is turbulent rather than laminar. Turbulence may be furtherincreased by using relatively high fluid flow rates and temperatures. Asanother alternative, additional inlet ports (not shown) may b-e formedinto the side walls and process fluids may enter the chamber via theseports as well as via manifold 18 so as to cause disruptions in the flowfrom the manifold 18. As yet another alternative, a megasonic transducerof a type that could withstand the etch fluids (e.g. sapphire,fluoroplastic, PFA, Halar, ECTFE, coated metal, orpolytetrafluoroethylene (PTFE) sold under the trade name Teflon) couldbe positioned in the chamber 10 to cause turbulent flow of the etchfluid and to thus induce or contribute to boundary layer thinning.

Post-Etch Quench and Rinse

At the end of the etch procedure, flow of etch solution is terminatedand a post-etch rinsing step may be carried out to remove etch solutionfrom the substrate and chamber. The post-etch rinsing step may beinitiated in one of several ways. In one example, manifold 18 is movedto the opened position (FIG. 1B), draining the etch solution from thechamber 10 into a drain (not shown), from which it is directed forcollection/disposal. The manifold is then closed and DI rinse water isintroduced into the chamber via fluid manifold 18 and caused to cascadethrough the chamber and over weir 34. Alternatively, the step of openingthe manifold 18 may be eliminated, in which case flow of DI water ispermitted to continue until the etch solution is thoroughly rinsed fromthe substrate, manifold and chamber.

As another alternative, the etch fluid may be rapidly removed fromchamber 10 by opening valve 27 a (FIG. 1C), causing the fluid to besuctioned into sealed negative pressure container 31 a for later re-useor disposal. As discussed in the “Structure” section above, this type ofrapid removal of etch solution minimizes etch variations across thesubstrate surface by more sharply ending the exposure of the substrateto the bulk etch fluid. This process is preferably enhanced bysimultaneously using the end effector 30 to withdraw the substrate fromthe chamber lower portion 12 a into the upper portion 12 b. Withdrawalmay be carried at any desired speed, although a rate of 25-300 mm/sechas been found beneficial.

The post-etch rinse process may preferably include a boundary layerthinning process to accelerate diffusion of the etch chemistry from thesurface of the substrate out of the boundary layer of fluid attached tothe substrate and into the surrounding bulk fluid. This diffusionprocess is known in the art as “quenching” and is instrumental interminating etching of the substrate surface. A megasonic transducerpositioned at or near the chamber bottom (e.g. a transducer provided aspart of fluid manifold 18, or a transducer mounted separately within thechamber, or the transducer of megasonics manifold 22) may also beutilized for this purpose.

The accelerated quench is preferably performed in combination with therapid removal of the bulk etch fluid (e.g. in approximately less than1.0 second), such as by suction of the fluid into the negative pressurecontainer 31 a (FIG. 1C) and the simultaneous withdrawal of thesubstrate into the upper portion 12 b of the chamber. However, any ofthe evacuation processes described above, such as opening of themanifold 18, may also be used preferably in combination with the liftingof the substrate from the chamber 10.

Next, the chamber 10 is rapidly filled with a quenchant such as DIwater. Since at this time the substrate is in the upper portion 12 b ofthe chamber, rapid filling can be performed without concern that thesubstrate will be splashed—an occurrence which could lead to lack ofuniformity across the substrate's surface. As the chamber 10 begins tofill, the megasonic transducer in the chamber bottom (i.e. depending onthe fluid handling system, this may be the transducer of manifold 22,manifold 18, or a lower chamber transducer) is operated at low power.The megasonic power is increased as the chamber fills with DI water.Once the lower portion 12 a of the chamber has been partially filled,the substrate is lowered into the quenchant. The turbulence created bythe megasonic energy facilitates boundary layer thinning that thusfacilitates diffusion of etch chemistry from the boundary layer into thebulk rinse water.

The megasonic power is increased as the volume of quenchant in thechamber increases. Beginning at a lower power and increasing the poweras the chamber fills minimizes the chance of high power megasonic energycausing splashing of quenchant onto the substrate, and also minimizesthe likelihood that residual etch solution on the substrate and in thetank would aggressively etch the bottom portion of the substrateimmersed in the water.

The flow of DI water or other quenchant into the chamber preferablycontinues even after the substrate is fully immersed. The uppermegasonic transducers 32 a, 32 b are energized. These transducers impartmegasonic energy into an adjacent region of the DI water. The energycreates a zone Z (FIGS. 2A through 2C) in which the turbulence createdby the megasonic energy causes boundary layer thinning and thusfacilitates gettering of the etch material away from the substrate andinto the quenchant. The zone Z is a band of megasonic energy extendingacross the chamber. The substrate transport 28 pulls the substratethrough zone Z so as to expose the entire substrate to the zone Z. Thearea of the band is preferably selected such that when the substratepasses through the zone, up to 30% of the surface area of a face of thesubstrate is positioned within the band. Most preferably, as the centerof the substrate passes through the zone, only approximately 3-30% ofthe surface area of a face of the substrate is positioned within theband.

The substrate is raised and lowered through zone Z one or more times asneeded for a thorough quench. The raising and lowering may be performedat any desired speed, although a rate of approximately 25-300 mm/sec hasbeen found to be beneficial. As the substrate passes from the upperregion 12 b into the bulk rinse fluid, particles entrained at thesubstrate surface are released at the gas/liquid interface and areflushed over the weir and out of the chamber. The expression “gas/liquidinterface” as used herein refers to the interface between air present inthe chamber (and/or gas or vapor introduced into the chamber) and fluidin the lower region 12 a of the chamber. Preferably the zone Z iscreated slightly below the gas/liquid interface.

It should be noted that the lower megasonic transducer may remainpowered on while the substrate is translated through the zone Z.

The quenching process may be enhanced by a stream of DI water preferablydirected into upper region 12 b through fluid applicators 37. As thesubstrate transport 28 pulls the substrate through the chamber, thesubstrate passes through zone Z and through the stream of fresh water.During movement of the substrate upwardly past the fluid stream, thefluid stream applies a thin layer of fresh rinse fluid to the portion ofthe substrate at which the boundary layer was just thinned by zone Z.The substrate may be moved upwardly and downwardly through the zone Zand the fluid stream one or more times as needed for a thorough quench.

The timing of energization of the transducers 32 a, 32 b may be selecteddepending on the goals of the process or the nature of the substratesurface (e.g. whether it is hydrophobic or hydrophilic). In someinstances it may be desirable to energize the transducers 32 a, 32 bonly during extraction of the substrate from lower region 12 a intoupper region 12 b, or only during insertion of the substrate into lowerregion 12 a, or during both extraction and insertion.

After quenching, DI water may continue to circulate through the chamberuntil such time as the chamber, end effectors and substrate have beenthoroughly rinsed.

Cleaning

A substrate cleaning step may also be performed utilizing the firstembodiment. If etching is performed, the cleaning step may occur beforeand/or after the etch process. Prior to cleaning, the chamber is drainedby moving the fluid manifold 18 away from the window 16. If the fluidhandling configuration of FIG. 1C is used, the megasonics manifold 22 ismoved to the closed position covering the opening. During the cleaningprocess, a cleaning solution (for example, a solution of water, NH₂OHand H₂O₂ that is known in the industry as “SC1”) is introduced into thechamber 10 via megasonics manifold 22 and caused to cascade over weir34. Alternatively, if a fluid handling configuration such as that shownin FIG. 1D is used, the cleaning solution enters the manifold 23 andchamber 10 via the appropriate one of the dedicated valves 33 c.

Megasonic transducers 32 a,b are energized during cleaning so as toimpart megasonic energy into an adjacent region of the process fluid—andin doing so create zone Z (FIGS. 2A through 2C) of optimum performancewithin the chamber. If necessary to prevent fine feature damage, one ofthe transducers may by operated at low power or zero power.

Throughout cleaning, the substrate transport 28 moves the substrateupwardly and downwardly one or more times (as required by the specificsof the process) to move the entire substrate through the zone Z ofoptimum performance. The substrate may be translated through the zone atany desired speed, although a rate of approximately 25-300 mm/sec hasbeen found beneficial.

As with the quenching process, the timing of energization of thetransducers 32 a, 32 b may be selected depending on the goals of theprocess. In some instances it may be desirable to energize thetransducers 32 a, 32 b only during extraction of the substrate fromlower region 12 a into upper region 12 b, or only during insertion ofthe substrate into lower region 12 a, or during both extraction andinsertion.

The zone Z is a band of megasonic energy extending across the chamber,preferably slightly below the gas/liquid interface. The substratetransport 28 pulls the substrate through the band so as to expose theentire substrate to the zone Z. The area of the band is preferablyselected such that when the substrate passes through the zone, up to 30%of the surface area of a face of the substrate is positioned within theband. Most preferably, as the center of the substrate passes through thezone, only approximately 3-30% of the surface area of a face of thesubstrate is positioned within the band.

Creation of zone Z is optimal for cleaning for a number of reasons.First, cleaning efficiency is enhanced by minimizing the thickness ofthe boundary layer of fluid that attaches to the substrate surface—sothat the cleaning solution can more effectively contact the substratesurface and so that reaction by products can desorb. The megasonicenergy from transducers 32 a, 32 b thin the boundary layer by creatingregional turbulence adjacent the substrate. Since transducers 32 a, 32 bare directed towards the front and back surfaces of the substrate, thisboundary layer thinning occurs on the front and back surfaces. Themegasonic energy further causes microcavitation within the fluid, i.e.formation of microbubbles that subsequently implode, releasing energythat dislodges particles from the substrate. The megasonic turbulencekeeps particles in the fluid suspended in the bulk and less likely to bedrawn into contact with the substrate. Lastly, high velocity fluid flowthrough the chamber and over the weir moves particles away from the zoneand thus minimizes re-attachment. This high velocity flow may beenhanced as discussed using a narrowed throat region in the upper end ofthe chamber, or using an active mechanism such as a bellows-type device,to accelerate fluid flow through the zone.

Further optimization of cleaning at zone Z may be achieved byintroducing a gas such as nitrogen, oxygen, helium or argon into upperinterior region 12 b via gas inlet port 38. The gas diffuses into thevolume of cleaning solution that is near the surface of the cleaningsolution and increases the microcavitation effect of the megasonictransducers in the zone Z of optimal performance.

The lower megasonic transducer associated with manifold 22 (or, in thecase of the FIG. 10 embodiment, a megasonic transducer associated withmanifold 23 or separately positioned in the lower portion of thechamber) may be activated during the cleaning process, to as to createan acoustic streaming effect within the chamber, in which streams ofmicrobubbles are formed that keep liberated particles suspended in thebulk fluid until they are flushed over the weir 34, so as to minimizeparticle re-attachment to the substrate. It has been found to bedesirable, but not required, to operate the lower megasonic transducerwhile the upper megasonic transducers 32 are also activated and whilethe substrate is being translated through the zone Z.

It should be noted that while some minimal boundary layer thinning maybe caused by activation of the lower transducer(s), boundary layerthinning is not the objective of activation of the megasonics associatedwith this transducer. Creating the zone Z in which the boundary layer isthinned as described above, rather than relying upon acoustic streamingprocedures for boundary layer thinning of the entire substrate surface,is advantageous in that by keeping the boundary layer relatively thickeroutside the zone, the chance of particle reattachment is minimized.

To further minimize the chance of particle reattachment, a particlegettering surface (not shown) may be positioned in the chamber near zoneZ. During cleaning, a charge is induced on the gettering surface suchthat particles liberated from the substrate surface are drawn to thegettering surface and thus away from the substrate. After the substratehas passed out of zone Z, the polarity of the gettering surface isreversed, causing release of particles from the gettering surface. Thesereleased particles are flushed out of the chamber 10 and into the weirby the flowing cleaning fluid.

A charge may also be induced on the end effector 30 so as to drawparticles off of the substrate when the end effector is in contact withthe substrate. Later, the polarity of the end effector is reversed,causing particles gettered into the end effector to be released into theflowing cleaning fluid in the chamber and to be flushed into the weir.

The cleaning process will result in release of gases from the cleaningsolution into the upper interior region 12 b, some of which may contactexposed regions of the substrate and cause pitting at the substratesurface. To avoid such exposure, select vapors are introduced into theupper chamber region 12 b via vapor inlet port 36. The vapors condenseon the substrate to form a protective film. If any released gas shouldcondense on the substrate, it will react with the protective film ratherthan reacting with the silicon surface of the substrate. For example, anSC1 cleaning solution will cause off-gassing of ammonia into thechamber. In this example, hydrogen peroxide vapor would be introducedinto the upper region 12 b to form a protective film on the substrate.Ammonia released by the cleaning solution will react with the protectivefilm rather than pitting the substrate surface.

After the substrate has been exposed to cleaning solution for therequired process time, the substrate is rinsed using a rinse solution.The rinse solution naturally will be dependent on the cleaning processbeing carried out. Following back end of the line (BEOL) cleaning, anisopropyl alcohol or dilute acid rinse may be carried out. After frontend cleaning process such as SC1 cleaning, a DI water rinse ispreferable. Rinsing may be accomplished in various ways. For example,with the substrate preferably elevated above the cleaning solution inthe chamber, the cleaning solution may be suctioned back through themanifold 22 into a low pressure container 31 b in the manner describedin connection with the etch process. Next, rinse fluid is introducedinto the chamber 10 (via, for example, manifold 22 of FIG. 1C, manifold23 of FIG. 1D) and cascades over the weir 34.

The substrate is lowered into the rinse water and the water rinses thecleaning solution from the chamber 10 and from the surface of thesubstrate. Alternatively, with the substrate remaining in the cleaningsolution, rinse fluid may be introduced into the lower region chamber,thereby flushing the cleaning solution from the chamber 10 into the weir34 as it rinses the chamber and substrate.

Megasonic energy from the side transducers 32 a, 32 b and/or the lowertransducer is optionally directed into the rinse water chamber so as toenhance the rinse process. The substrate may be passed through zone Zmultiple times (again at a rate that may, but need not be, within therange of 25-300 mm/sec) as needed for thorough rinsing. A gas such asnitrogen, oxygen, helium or argon may be introduced into upper interiorregion 12 b via gas inlet port 38. The gas diffuses into the volume ofrinse fluid that is near the gas/liquid interface (i.e. the interfacebetween the upper surface of the rinse fluid and the gas or air aboveit) and surface of the rinse fluid and increases the microcavitationeffect of the megasonic transducers in zone Z.

The power state of the transducers is selected as appropriate for thestage of the rinsing process and the surface state of the substrate.Preferably, both of the side transducers 32 a, 32 b and the lowertransducer are powered “on” during insertion of the substrate into therinse fluid. Depending upon the surface state of the substrate (e.g.whether it is hydrophilic or hydrophobic), the side transducers 32 a, 32b may be on or off during extraction of the substrate into the upperregion 12 b.

Reactive Gas Rinse

At some point during wet processing, the substrate may be exposed to areactive gas (such as, for example, ozone, chlorine or ammonia) so as tointeract with the substrate surface. Preferably, the reactive gas isdissolved in a rinse fluid and the substrate is exposed to the rinsefluid for an appropriate length of time.

The reactive gas rinse may be carried out with megasonic energy beingused to create a turbulent flow of the reactive gas rinse fluid. Theturbulent flow thins the boundary layer of fluid attached to thesubstrate, so as to enhance reactive gas diffusion through the boundarylayer into contact with the substrate surface. Turbulence may be createdusing a megasonic transducer positioned in the bottom of the chamber asreactive gas rinse fluid flows into the chamber via one of the fluidmanifolds. Alternatively, reactive gas may be introduced, via nozzles 36or additional nozzles, into the upper interior 12 b of the chamber asrinse water flows into the chamber via one of the fluid manifolds. Thegas dissolves into the rinse water near the surface of the rinse water.The upper megasonic transducers 32 a, 32 b are energized to causeboundary layer thinning in zone Z, creating a zone of optimal absorptionof reactive species onto the substrate surface. The substrate istranslated through the zone Z one or more times as needed for thereactive gas to effectively treat the substrate surface.

Pre-Dry Rinse

In certain processes it may be desirable to perform a pre-drypassivating rinse using hydrofluoric acid (HF), hydrochloric acid (HCl)or de-gassed DI water.

In such processes, the lower portion 12 a of the chamber 10 is filledwith passivation fluid. The passivation fluid may be injected into a DIwater stream entering fluid manifold 18 (using, for example, the fluidhandling configuration shown in FIG. 1C), causing it to flow into thechamber 10 with the DI water. Alternatively, the passivation fluid mayflow directly into manifold 18 and into chamber, or, if the fluidhandling configuration of FIG. 1D is used, the fluid may enter manifold23 and chamber 10 via dedicated valve 33 b. In either case, the solutioncascading over weir 34 may be recirculated back into the chamber 10throughout the pre-dry rinse process, such as by collecting it into a(preferably) temperature-controlled vessel and circulating it back tomanifold 18 for re-introduction into the chamber 10. Alternatively, thepre-dry rinse process may be a “one-pass” process in which theoverflowing fluid is directed to a drain for disposal. As a thirdalternative, the flow of fluid may be terminated once the lower portion12 a of the chamber has been filled.

Substrate S is engaged by end effector 30 and moved into the solution bythe substrate transport device 28. Substrate S is positioned in thelower portion 12 a of the chamber, i.e. at an elevation below that ofthe weir 34, so that the substrate is fully immersed in the passivationsolution. As with the reactive gas step, the upper megasonic transducers32 a, 32 b may be energized to cause boundary layer thinning in zone Z,creating an optimal zone for contact between the passivating rinse fluidand the substrate surface. The substrate is translated through the zoneZ one or more times as needed for the passivating rinse fluid toeffectively passivate the substrate surface. The use of megasonic energymay also prevent particle deposition onto the substrate, which can oftenoccur using low-pH passivation solutions such as HF or HCl.

Drying

After the final treatment and rinse steps are carried out, the substrateis dried within the chamber. Drying may be performed in a number ofways—three of which will be described below. Each of the three examplesdescribed utilize an IPA vapor preferably carried into the chamber by anitrogen gas flow. In each example, the IPA vapor is preferablygenerated in an IPA generation chamber remote from the chamber 10, usingone of a variety of IPA generation procedures known those skilled in theart. For example, IPA vapor may be created within the IPA generationchamber by injecting a pre-measured quantity of IPA liquid onto a heatedsurface within the IPA generation chamber. The IPA is heated on theheated surface to a temperature preferably less than the boiling pointof IPA (which is 82.4° C. at 1 atmosphere). Heating the IPA increasesthe rate at which IPA vapor is generated and thus expedites the process,creating an IPA vapor cloud. When the IPA vapor is needed in the chamber10, nitrogen gas is passed through an inlet into the IPA generationchamber, and carries the IPA vapor out of the IPA generation chamber viaan outlet that is fluidly coupled to the vapor inlet port 36 in chamber10.

The three examples of drying processes using the IPA vapor will next bedescribed. In one embodiment, the bulk water used for the final rinsemay be rapidly discharged from the chamber 10 by rapidly withdrawing thefluid into a negative pressure container, or by performing a “quickdump” by moving megasonics manifold 22 to the opened position (or, ifdrying follows an HF last process and rinse, fluid manifold 18 is movedfrom the closed to opened position). Then a vapor of isopropyl alcoholis introduced into the chamber 10 via vapor inlet port 36. The IPA vaporpasses into the lower portion 12 a of the chamber and condenses on thesurface of the substrate where it reduces the surface tension of thewater attached to the substrate, and thus causes the water to sheet offof the substrate surfaces. Any remaining liquid droplets may beevaporated from the substrate surface using gas, such as heated nitrogengas, introduced through gas inlet port 38. Gas inlet port 38 may includea gas manifold having outlets that are angled downwardly. The endeffector 30 may be used to move the substrate past this manifold toaccelerate evaporation of remaining IPA/water film from the surface ofthe substrate.

In an alternative drying process, an atmosphere of IPA vapor may beformed in the upper interior region 12 b by introducing the vapor viavapor inlet port 36. According to this embodiment, the substratetransport 28 lifts the substrate from the lower interior region 12 ainto the IPA atmosphere in the upper interior region 12 b, where the IPAvapor condenses on the surface of the substrate, causing the surfacetension of the water attached to the substrate to be reduced, and thuscausing the water to sheet from the substrate surface.

The megasonic transducers 32 a, 32 b may be energized as the substrateis pulled from the DI water so as to create turbulence in zone Z to thinthe boundary layer of fluid attached to the substrate. With the boundarythinned by zone Z. IPA can diffuse more quickly onto the surface of thesubstrate, thus leading to faster drying with less IPA usage. Thus, thesubstrate may be withdrawn into the IPA atmosphere relatively quickly,i.e. preferably at a rate of 30 mm/sec or less, and most preferably at arate of between approximately 8 mm/sec-30 mm/sec. This is on the orderof ten times faster than prior extraction drying methods, which utilizea slow withdrawal (e.g. 0.25 to 5 mm/sec) to facilitate asurface-tension gradient between fluid attached to the substrate and thebulk rinse water.

Again, gas such as heated nitrogen may be introduced via manifold 38 toevaporate any remaining IPA and/or water film, and the substrate may betranslated past the manifold 38 to accelerate this evaporation process.

In a third alternative embodiment, slow extraction-type drying may beutilized. The substrate may thus be slowly drawn from the bulk DI waterinto the IPA vapor. Using this embodiment, the IPA condenses on theliquid meniscus extending between the substrate and the bulk liquid.This results in a concentration gradient of IPA in the meniscus, andresults in so-called Marangoni flow of liquid from the substratesurface. Gas such as heated nitrogen gas may be directed from manifold38 onto the substrate to remove some of the residual water and/or IPAdroplets and/or film. The substrate may be moved past gas manifold 38 toaccelerate this evaporation step.

In each of the above three embodiments, care should be taken to maintainthe static pressure within the chamber during the various steps in thedrying processes.

Second Embodiment—Structure

FIG. 3A shows a second embodiment 100 of a single substrate processingchamber utilizing principles of the present invention.

Second embodiment 100 generally includes a process chamber 102, acontainment vessel 104, an end effector 106 (see FIG. 6), a rotationalactuator 108 and a vertical actuator 110.

Referring to FIG. 3A, process chamber 102 includes closely spacedchamber walls 111 defining a lower interior region 113 a and an upperinterior region 113 b. An overflow weir 114 is positioned in the lowerregion 113 a, slightly below upper region 113 b. Overflow weir 114includes a wall section 115 over which fluids cascade into the weir 114during certain processing steps. At the bottom of the chamber 102 is alower opening 135, and at the top of the chamber is an upper opening 142(FIG. 4).

A vapor/gas manifold 116 is provided for directing vapors/gases intoupper region 113 b of the chamber. Manifold 116 (best shown in FIG. 4)includes walls 120 on opposite sides of upper region 113 b. Vapor/gasports 122 a (see FIG. 4), 122 b (see FIG. 5) extend through walls 120and are fluidly coupled to vapor/gas conduits 124 a, 124 b. A pluralityof orifices 126 a, 126 b extend from conduits 124 a, 124 b into thechamber 102. The orifices 126 a, 126 b may be downwardly angled asshown. The angles are preferably (but are not required to be) within therange of 45°-80° relative to the normal to walls 120. Each port 122 a,122 b is coupled to plumbing that delivers process vapors/gases throughthe ports 122 a,b and into chamber 102 via conduits 124 a, b andorifices 126 a, 126 b.

Referring to FIG. 5, manifold 116 additionally includes drain ports 128extending from overflow weirs 114. Drain ports 128 are fluidly coupledto plumbing (not shown) that carries overflow fluids from weir 114 andaway from the chamber for recirculation or disposal.

Within containment vessel 104 is a fluid manifold 130, which includes anelongated conduit 132, and a plurality of openings 134 extending fromconduit 132 into the lower region of the chamber 102. Fluid ports 133are coupled to conduit 132 and are fluidly coupled to a network ofplumbing. This plumbing network selectively delivers a selection ofdifferent process chemistries through the fluid ports 133 into manifold130 and thus into the chamber 102. Manifold 130 is moveable to an openedposition as shown in FIG. 3B to permit fluid in the chamber to berapidly discharged through lower opening 135 into a drain (not shown).Automation 137 is provided for moving the fluid manifold between theopen and closed position.

An end effector of the type shown in FIG. 6 may be used for either ofthe first or second embodiments. End effector 136 includes a block 138and a pair of gripping members 140 that engage a substrate S betweenthem by engaging opposite edges of the substrate as shown. Verticalactuator 110 (FIG. 3A) moves block 138 and gripping members 140 betweena withdrawn position in which the substrate S is fully removed from thechamber 102, and an advanced position in which the substrate S is fullydisposed within the lower region 113 a. When in the advanced position,block 138 closes against opening 142 (FIG. 4) of chamber 102 so as tocontain gases and vapors and so as to prevent migration of particlesinto the chamber.

When the end effector is in the withdrawn position, rotational actuator108 (FIG. 3A) is configured to rotate the end effector to a lateralorientation. This is particularly desirable for large substrates (e.g.300 mm) that are customarily housed in a horizontal arrangement in astorage device or carrier. The end effector can be made to retrieve anddeposit substrates directly from/to such a carrier, or from a separaterobotic end effector provided for unloading/loading substrates from/tothe carrier. The vertical and horizontal actuators preferably utilizeconventional robotics of the type known to those of skill in the art,and these as well as other automated features (e.g. those relating tomeasurement and injection of process fluids/vapors/gases are controlledby a conventional controller such as a PLC controller.

FIGS. 7A through 7E show an alternative end effector 106 a having anengaging mechanism found particularly beneficial when used with thedescribed embodiments. An alternative chamber having a different shapethan the chamber 102 is also described, although various other chambershapes may be utilized with the end effector 106 a. As will beunderstood from the description that follows, the end effector 106 a hastwo positions relative to the substrate: a transport position in whichthe substrate is securely held by the end effector, and a processposition in which the end effector stabilizes the substrate whilepermitting process fluids to flow into contact with the substrate'ssurface.

Referring to FIG. 7A, the end effector 106 a includes a pair of supportmembers 150, each of which includes an upper support 152, lower support154, upper transport slot 156 and lower transport slot 158. Duringtransport of the substrate, upper and lower transport slots 156, 158receive the edge of the substrate S as shown in FIGS. 7A and 7B, therebysupporting the substrate as it is moved into/out of/within the chamber102 a.

As illustrated in FIGS. 7B-7D, a bottom notch 160 is mounted within thechamber 102 a (for example, to a chamber wall 111 a as shown). As thesubstrate is lowered into the process position in the chamber, thebottom edge of the substrate contacts bottom notch 160. Continueddownward movement of the end effector 106 causes the substrate to edgeto slip out of the upper and lower transport slots 156, 158. Once thesubstrate has been fully lowered into the process position within thechamber (FIG. 7D), its weight is supported by the bottom notch 160 andsupport members 152, 154 function to stabilize the substrate in thisprocess position. Specifically, as illustrated in FIG. 7E, the substrateedge is disposed between a slot in support member 152, which restrictsforward/backward movement of the substrate but preferably does not gripthe substrate—thereby keeping the substrate stable while allowingprocess fluid to flow through the slot. Support member 154 (whichpreferably does not include a slot) extends towards the substrate edgeand restricts lateral movement of the substrate.

Because the chamber walls 111 a are closely spaced, the chamber wallspreferably include recessed sections 162 (FIGS. 7B-7D) which provideadditional space for receiving end effector members 150.

Second Embodiment—Operation

As with the first embodiment, the second embodiment may be used for avariety of steps, including but not limited to wet etch, clean, rinseand drying operations either alone or in combination with one another orwith other process steps. Operation of the second embodiment will bedescribed in the context of an etch, clean and drying process, withrinses being performed following etching and cleaning. However it shouldbe understood that various other combinations of processes might beperformed without departing from the scope of the present invention. Itshould also be understood that various steps described in connectionwith the first embodiment may be practiced using the second embodiment,including the described methods for boundary layer thinning,megasonic-assisted quenching, cleaning, rinsing and/or drying, ozonepassivation, chemical injection and exhaustion. Moreover, the rates andother values given as examples in connection with the first embodimentmay also be applied to use of the second and third embodiments.

Operation of the second embodiment begins with fluid manifold 130 in theclosed position as shown in FIG. 5. DI water is directed into fluidports 133, through manifold conduit 132 and into the chamber 102 throughopenings 134. The DI water passes through the lower interior region 113a and cascades over wall 115 into weir 114 and out drain ports 128. Atthe same time, nitrogen gas flows slowly into the uppermost of the fillports 122 a,b in the vapor/gas manifold, causing the nitrogen gas toflow through the associated conduits 124 a, 124 b and into the upperregion 113 b of the chamber 102 via orifices 126 a, 126 b. This low flowmaintains a slight positive pressure within the chamber 102. Preferably,this nitrogen flow continues throughout etching, cleaning, rinsing anddrying.

Substrate W is engaged by end effector 106 and moved into the cascadingDI water by the automation system. Substrate S is positioned in thelower interior 113 a of the chamber. Process fluids necessary for theetching procedure (e.g. HF) are injected into the DI water beingdelivered to fluid ports 133 into manifold, and are thus passed into thechamber 102 via fluid manifold 130. At the end of the etch procedure,delivery of etch solution into the chamber 102 is terminated. The etchsolution may be exhausted from the chamber and rinsing may be carriedout preferably using one of the rinse procedures described above. Forexample, pure DI water may continue to flow into the chamber 102 toflush the etch solution from the chamber and to rinse the substrate,manifold, and chamber.

In an alternative etch procedure, the lower interior 113 a may be filledwith etch solution, and then the substrate lowered into the staticvolume of etch solution. After the required dwell time, a cascadingrinse or other type of rinse is preferably carried out as describedabove.

Once the substrate is thoroughly rinsed, a cleaning solution (forexample, a solution of water, NH₂OH and H₂O₂ that is known in theindustry as “SC1” is introduced into the chamber 102 via manifold 130and caused to cascade over wall 115 into weir 114. After the substratehas been exposed to the cleaning solution for the desired period oftime, injection of the cleaning solution into the DI stream isterminated, and pure DI water flows into the chamber 102 to rinse thesubstrate.

After the final treatment and rinse steps are carried out, the substrateis dried within the chamber 102. Drying may be performed in a number ofways—each of which preferably utilizes IPA vapor generated in a mannersimilar to that described above.

In one example of a drying process, the bulk water used for the finalrinse may be rapidly discharged from the chamber 102 by moving fluidmanifold 130 to the opened position (FIG. 3B). A vapor of isopropylalcohol is then introduced into the upper portion 113 b of the chamberby passing the IPA vapor through the vapor/gas inlet port 122 a,b, intothe corresponding conduit 124 a,b and thus into the chamber via openings126 a,b. The IPA vapor flows into lower portion 113 a of the chamber,where it condenses on the surface of the substrate where it reduces thesurface tension of the water attached to the substrate, and thus causesthe water to sheet off of the substrate surfaces. Any remaining liquiddroplets may be evaporated from the substrate surface using a gas (e.g.heated nitrogen gas) introduced through the vapor/gas inlet ports 126a,b.

Alternatively, an atmosphere of IPA vapor may be formed in the upperinterior region 113 b by introducing the vapor via gas/vapor openings126 a,b. According to this embodiment, the end effector 106 lifts thesubstrate from the lower interior region 113 a into the IPA atmospherein the upper interior region 113 b. Withdrawal of the substrate into theIPA atmosphere may occur quickly, i.e. approximately 8 to 30 mm/sec. TheIPA vapor condenses on the surface of the substrate, causing the surfacetension of the water attached to the substrate to be reduced, and thuscausing the water to sheet from the substrate surface. A third openingsimilar to openings 126 a,b may be provided just above overflow weir 114to allow a vacuum to be applied so as to accelerate evaporation of theIPA or IPA/water mixture. Again, gas such as heated nitrogen may beintroduced to dry remaining IPA and/or droplets/film from the substrate.

As another alternative, the substrate may be slowly drawn from the bulkDI water into the IPA vapor. Using this embodiment, the IPA condenses onthe liquid meniscus extending between the substrate and the bulk liquid.This results in a concentration gradient of IPA in the meniscus, andresults in so-called Marangoni flow of liquid from the substratesurface. Gas (e.g. heated nitrogen gas) may be used following theMarangoni process to remove any residual water droplets.

Third Embodiment—Structure

Referring to FIG. 8, a third embodiment 200 of a single substrateprocessing chamber includes a chamber 210 having a lower interior region212 a proportioned to receive a substrate S for processing, an upperinterior region 212 b, and an opening 214 in the upper interior region212 a.

A substrate transport device (not shown) is provided and includes an endeffector configured to engage a substrate S, preferably in the mannershown in FIG. 6. The transport device is driven by conventionalautomation (not shown) to move the substrate S through opening 214 into,out of, and within the chamber 210 in an edgewise direction.

A lid 215 is provided for sealing opening 214. The lid 215 may beoperable with the automation that also drives the end effector, or withseparate automation.

A fluid handling system (not shown) is configured to carry variousprocess fluids (e.g. etch fluids, cleaning fluids, rinse water, etc.)into the lower interior region 212 a of the chamber 210. The fluidhandling system may take a variety of forms, including those describedwith respect to FIGS. 1A-1D, and 5.

One or more megasonic transducers (not shown) are provided in the lowerregion 212 a of the chamber 210. The lower transducer may be mounted tothe walls of the chamber 210 in a manner known in the art, or it maycomprise a portion of a manifold assembly as described above. When thelower megasonic transducer directs megasonic energy into fluid in thechamber, it induces acoustic streaming within the fluid—i.e. streams ofmicrobubbles that aid in removal of contaminants from the substrate bykeeping particles in motion within the process fluid so as to avoidtheir reattachment to the substrate.

Vapor inlet ports, fluid applicators, and gas manifolds extend into theupper interior region 212 b of the chamber 210. Each is fluidly coupledto a system of conduits that deliver the appropriate fluids, vapors andgases to the ports as needed during processing.

An upper overflow weir 234 is positioned below the opening 214. Processfluid flowing through the chamber and past substrate S cascades into theweir 434 and into overflow conduits 235 for recirculation back into thefluid handling system and re-introduction into the chamber, or intodrain 233. One more megasonic transducers 232 (one shown in FIG. 8),which may include a single transducer or an array of multipletransducers, is positioned at an elevation below that of the weir 234,and is oriented to direct megasonic energy into an upper portion of thechamber 210.

The energy interacts with the substrate as the substrate is movedupwardly and downwardly though the chamber 210 by the end effector. Itis desirable to orient the transducer such that its energy beaminteracts with the substrate surface at or near the surface of theprocess fluid, e.g. at a level within the top 0-20% of the chamberregion lying below the elevation of upper weir 234. The transducers maybe configured to direct megasonic energy in a direction normal to thesubstrate surface or at an angle from normal. Preferably, energy isdirected at an angle of approximately 0-30 degrees from normal, and mostpreferably approximately 5-30 degrees from normal. The power andorientation of the transducer(s) may be adjustable in the mannerdescribed in connection with the first embodiment.

When energized, the transducer 232 creates a zone Z (see FIGS. 2A-2C) ofoptimal performance within the process fluid in the chamber. As will bediscussed in greater detail below, energization of the zone enhancespost-etch quenching, cleaning, rinsing and drying processes throughregional boundary layer thinning and microcavitation. A lower weir 240is positioned beneath the elevation of the transducer 232. Lower weir240 optionally includes a door 242 having a closed position, whichprevents flow of fluid into the weir. When weir 240 is in the closedposition, fluid flowing into the chamber flows past transducer 232 andcascades over upper weir 234. When lower weir 240 is in the openedposition, fluid flowing into the chamber cascades through weir 234 anddoes not flow Into contact with transducer 232. The lower weir 240 isused to shunt away harsh chemicals (such as an etch solution utilizinghydrofluoric acid) that can damage the megasonic transducer. Althoughsome transducer materials such as sapphire or Teflon can resist theharsh effects of such chemicals, those materials are very expensive andwill increase the overall cost of the chamber. Moreover, providing aseparate weir for harsh chemicals also helps to keep those chemicals outof conduits used to carry other solutions, such as the conduits 235 thatre-circulate cleaning and rinsing solutions, and thus minimizescross-contamination of fluids.

Third Embodiment—Operation

Use of the chamber 200 will be described in the context of an etch,clean and drying process, in which rinses are performed followingetching and cleaning. Naturally, various other combinations of these orother process steps may be performed without departing from the scope ofthe present invention.

Etching

An etch operation preferably begins with the lower portion 212 a of thechamber 210 filled with process fluids necessary for the etchingprocedure (for example hydrofluoric acid (HF), ammonium fluoride and HF,or buffered oxide). These fluids are introduced via the fluid handlingsystem that directs process fluids into the lower end of the chamber.

A substrate S is engaged by the end effector (such as end effector 30 ofFIG. 6) and is moved into the etch solution. Substrate S is positionedin the lower portion 212 a of the chamber such that its upper edge isbelow the elevation of lower weir 240. If provided, the door 242 oflower weir 240 is moved to the opened position. Etch solution continuesflowing into the chamber 210, and cascades into weir 240.

The etch preferably includes boundary layer thinning to assist the etchsolution in reaching and thus reacting with the substances that are tobe removed from the substrate surface. Boundary layer thinning may beaccomplished by inducing turbulence in the flowing etch fluid usingdisturbances formed into the sidewalls of the chamber. The inducedturbulence may be enhanced using relatively high fluid flow rates andtemperatures for the etch solution. Other mechanisms for inducingturbulence in the etch solution, including those described in connectionwith the first and second embodiments, may also be utilized.

Post-Etch Quench and Rinse

At the end of the etch procedure, flow of etch solution is terminatedand a post-etch rinsing step may be carried out to remove etch solutionfrom the substrate and chamber.

The post-etch rinse process preferably includes a quenching process,which accelerates diffusion of the etch chemistry from the surface ofthe substrate out of the boundary layer of fluid attached to thesubstrate and into the surrounding bulk fluid. Quenching is preferablyinitiated using a rapid removal (e.g. in preferably, but not limited to,less than approximately 1.0 second), of etch solution from the lower endchamber 210, such as using sealed pressure chambers such as the chambers31 a described in connection with FIG. 1C. Quickly removing the bulketch solution from the chamber minimizes etch variations across thesubstrate surface by more sharply ending the exposure of the substrateto the bulk etch fluid. This process is preferably enhanced bysimultaneously withdrawing the substrate from the chamber lower portion212 a into the upper portion 212 b using the substrate transport.

Next, the lower weir 240 is moved the closed position and the chamber210 is rapidly filled with a quenchant such as DI water. Since at thistime the substrate is in the upper portion 212 b of the chamber, rapidfilling can be performed without concern that the substrate will besplashed—an occurrence which could lead to lack of uniformity across thesubstrate's surface. As the chamber 210 begins to fill, the megasonictransducer in the chamber bottom is operated at low power. Once thelower portion 212 a of the chamber has been partially filled, thesubstrate is lowered into the quenchant. The turbulence created by themegasonic energy facilitates boundary layer thinning that thusfacilitates diffusion of etch chemistry from the boundary layer into thebulk rinse water.

The megasonic power is increased as the volume of quenchant in thechamber increases. Beginning at a lower power and increasing the poweras the chamber fills minimizes the chance of high power megasonic energycausing splashing of quenchant onto the substrate, and also minimizesthe likelihood that residual etch solution on the substrate and in thetank would aggressively etch the bottom portion of the substrateimmersed in the water.

The flow of DI water or other quenchant into the chamber preferablycontinues even after the substrate is fully immersed. Because lower weir240 is closed, the fluid level rises above megasonic transducer 232 andcascades into upper weir 234. The upper megasonic transducer 232 isenergized and imparts megasonic energy into an adjacent region of the DIwater in zone Z (FIGS. 2A through 2C). In zone Z, the turbulence createdby the megasonic energy causes boundary layer thinning and thusfacilitates gettering of the etch material away from the substrate andinto the fresh quenchant. The substrate is pulled through zone Z and israised and lowered through zone Z one or more times as needed for athorough quench. As with prior embodiments, the area of the band ispreferably selected such that when the substrate passes through thezone, up to 30% of the surface area of a face of the substrate ispositioned within the band. Most preferably, as the center of thesubstrate passes through the zone preferably approximately 3-30% of thesurface area of one face of the substrate is positioned within the band.

As the substrate is lowed from the upper region 212 b into the bulkrinse fluid, particles entrained at the substrate surface are releasedat the air/liquid interface and are flushed over the weir and out of thechamber 210.

The quenching process may be enhanced by a stream of DI water preferablydirected into upper region 212 b through fluid applicators (such asapplicators 37 described in connection with the first embodiment)located in the upper region. As the substrate transport pulls thesubstrate through the chamber, the substrate passes through zone Z andthrough the stream of fresh water. During movement of the substrateupwardly past the fluid stream, the fluid stream applies a thin layer offresh rinse fluid to the portion of the substrate at which the boundarylayer was just thinned by zone Z. The substrate may be moved upwardlyand downwardly through the zone Z and the fluid stream one or more timesas needed for a thorough quench.

As previously discussed, the timing of energization of the transducers232 may depend on the goals of the process or the nature of thesubstrate surface (e.g. whether it is hydrophobic or hydrophilic). Insome instances it may be desirable to energize the transducers 232 onlyduring extraction of the substrate from lower region 212 a into upperregion 212 b, or only during insertion of the substrate into lowerregion 212 a, or during both extraction and insertion.

After quenching, DI water may continue to circulate through the chamberuntil such time as the chamber, end effectors and substrate have beenthoroughly rinsed.

Cleaning

Prior to cleaning, the chamber is drained in using one of a variety ofmethods, including one of the methods described above. During thecleaning process, a cleaning solution (e.g. an “SC1” solution or aback-end cleaning solution) is introduced into the chamber 210 using thefluid handling system. Lower weir 240 remains in closed position andthus allows the cleaning fluid to rise above transducer 232 and tocascade over upper weir 234.

Megasonic transducer 232 is energized during cleaning so as to impartmegasonic energy into zone Z. The substrate transport moves thesubstrate upwardly and downwardly one or more times in an edgewisedirection to move the entire substrate through the zone Z. As with thequenching process, the timing of energization of the transducers 232 maybe selected depending on the goals of the process.

The zone Z optimizes cleaning for a number of reasons. First, cleaningefficiency is enhanced by creating regional turbulence that thins theboundary layer and thus allows the cleaning solution to effectivelycontact the substrate surface. The megasonic energy further causesmicrocavitation within the fluid, i.e. formation of microbubbles thatsubsequently implode, releasing energy that dislodges particles from thesubstrate. Microcavitation may be enhanced by introducing a gas such asnitrogen, oxygen, helium or argon into upper interior region 212 b via agas inlet port, such that the gas diffuses into the volume of cleaningsolution that is near the surface of the cleaning solution.

Second, the megasonic turbulence also keeps particles in the fluidsuspended in the bulk and less likely to be drawn into contact with thesubstrate. Finally, high velocity fluid flow through the chamber andover the weir moves particles away from the zone and thus minimizesre-attachment.

A megasonic transducer in the lower region 212 b may be activated duringthe cleaning process, so as to create an acoustic streaming effectwithin the chamber, keeping liberated particles suspended in the bulkfluid until they are flushed over the weir 234. This minimizes thechance of particle reattachment. To further minimize the chance ofparticle reattachment, a particle gettering surface (not shown) may bepositioned in the chamber near zone Z. During cleaning, a charge isinduced on the gettering surface such that particles liberated from thesubstrate surface are drawn to the gettering surface and thus away fromthe substrate. After the substrate has passed out of zone Z, thepolarity of the gettering surface is reversed, causing release ofparticles from the gettering surface. These released particles areflushed out of the chamber 10 and into the weir by the flowing cleaningfluid.

The cleaning process will result in release of gases from the cleaningsolution into the upper interior region 212 b, some of which may contactexposed regions of the substrate and cause pitting at the substratesurface. To avoid such exposure, select vapors are introduced into theupper region 212 b via a vapor inlet port so as to form a protectivefilm on the substrate. If reactive gases released from the cleaningsolution condense on the substrate, they will react with the protectivefilm rather than reacting with the silicon surface of the substrate. Forexample, an SC1 cleaning solution will cause off-gassing of ammonia intothe chamber. In this example, hydrogen peroxide vapor would beintroduced into the upper region 212 b to form a protective film on thesubstrate. Ammonia released by the cleaning solution will react with theprotective film rather than pitting the substrate surface.

After the substrate has been exposed to cleaning solution for therequired process time, the substrate is rinsed using a rinse solution.The rinse solution naturally will be dependent on the cleaning processbeing carried out. Rinsing may be accomplished in various ways. In oneexample, the substrate is elevated above the cleaning solution in thechamber and the cleaning solution is withdrawn from the chamber using alow pressure container such as container 31 b described above. Rinsefluid is introduced into the chamber 210 and cascades over the upperweir 234.

The substrate is lowered into the rinse fluid and the fluid rinses thecleaning solution from the chamber 210 and from the surface of thesubstrate. Megasonic energy from the side transducers 232 and/or a lowertransducer is optionally directed into the chamber so as to enhance therinse process. The substrate may be passed through zone Z multiple timesas needed for thorough rinsing. A gas such as nitrogen, oxygen, heliumor argon may be introduced into upper interior region 212 b. The gasdiffuses into the volume of rinse fluid that is near the gas/liquidinterface (i.e. the interface between the upper surface of the rinsefluid and that gas above it) and increases the microcavitation effect ofthe megasonic transducers in zone Z.

The power state of the transducers is selected as appropriate for thestage of the rinsing process and the surface state of the substrate.Preferably, the side transducer 232 and the lower transducer are powered“on” during insertion of the substrate into the rinse fluid. Dependingupon the surface state of the substrate (e.g. whether it is hydrophilicor hydrophobic), the side transducer 232 may be on or, off duringextraction of the substrate into the upper region 12 b.

Drying

The final rinse may be followed by any of a variety of drying processes,including (but not limited to) those described in connection with thefirst and second embodiments.

Three embodiments utilizing principles of the present invention havebeen described. These embodiments are given only by way of example andare not intended to limit the scope of the claims—as the apparatus andmethod of the present invention may be configured and performed in manyways besides those specifically described herein. Moreover, numerousfeatures have been described in connection with each of the describedembodiments. It should be appreciated that the described features may becombined in various ways, and that features described with respect toone of the disclosed embodiments may likewise be included with the otherembodiments without departing from the present invention.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. An apparatus for treating at least one substrate, comprising: achamber having an opening in an upper portion of the chamber, whereinthe opening is sized to receive the at least one substrate, and aprocessing region proportioned to receive the at least one substrate,wherein the processing region has a lower interior portion and an upperinterior portion; means for causing turbulent flow, wherein the meansfor causing turbulent flow is coupled to the chamber in one or both ofthe lower interior region and the upper interior region; an inlet and anoutlet coupled to the chamber and in fluid communication with the lowerportion of the chamber; and an upper overflow weir and a lower overflowweir positioned at an elevation below the upper overflow weir.
 2. Theapparatus of claim 1, further comprising an end effector.
 3. Theapparatus of claim 1, wherein the means for causing turbulent flowcomprises a megasonic transducer.
 4. The apparatus of claim 3, whereinthe megasonic transducer is oriented to propogate energy in a directionnormal to the substrate surface.
 5. The apparatus of claim 3, whereinthe megasonic transducer is oriented to propagate energy at an anglethat is less than normal to the substrate surface.
 6. The apparatus ofclaim 1, further including a source of heated gas fluidly coupled to thechamber to volatize fluid from a surface of a substrate.
 7. Theapparatus of claim 6, further including one or more inlets in thechamber for introduction of the heated gas into the chamber, and an endeffector having a substrate-receiving portion moveable to translate asubstrate past the inlets to accelerate evaporation.
 8. The apparatus ofclaim 1, further comprising a vapor exhaust system for exhausting dryingvapor from the system.
 9. The apparatus of claim 1, wherein the chamberis proportioned to process only one substrate at a time.
 10. Theapparatus of claim 1, wherein the source of process fluid is fluidlycoupled to the lower portion of the chamber, and wherein the source ofprocess fluid is moveable away from the lower portion.
 11. The apparatusof claim 1, wherein the upper and lower overflow weirs have three portscoupled thereto.
 12. An apparatus for treating at least one substrate,comprising: a chamber having an opening in an upper portion of thechamber, wherein the opening is sized to receive the at least onesubstrate, and a processing region proportioned to receive the at leastone substrate, wherein the processing region has a lower interiorportion and an upper interior portion; means for causing turbulent flow,wherein the means for causing turbulent flow is coupled to the chamberin one or both of the lower interior region and the upper interiorregion; an inlet and an outlet coupled to the chamber and in fluidcommunication with the lower portion of the chamber; one or moreoverflow weirs; and three ports coupled with the one or more overflowweirs.
 13. The apparatus of claim 12, further comprising an endeffector.
 14. The apparatus of claim 12, wherein the means for causingturbulent flow comprises a megasonic transducer.
 15. The apparatus ofclaim 14, wherein the megasonic transducer is oriented to propogateenergy in a direction normal to the substrate surface.
 16. The apparatusof claim 12, wherein the chamber is proportioned to process only onesubstrate at a time.
 17. The apparatus of claim 12, wherein the sourceof process fluid is fluidly coupled to the lower portion of the chamber,wherein the source is moveable away from the lower portion.
 18. Theapparatus of claim 12, further including a source of heated gas fluidlycoupled to the chamber to volatize fluid from a surface of a substrate.19. The apparatus of claim 18, further including one or more inlets inthe chamber for introduction of the heated gas into the chamber, and anend effector having a substrate-receiving portion moveable to translatea substrate past the inlets to accelerate evaporation.
 20. The apparatusof claim 18, further comprising a vapor exhaust system for exhaustingdrying vapor from the system.